• The Journal of Korean Academy of Prosthodontics
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• v.18 no.1
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• pp.73-86
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• 1980

Recently, the controversy continues as to whether maximum intercuspation of teeth should occur at the terminal hinge position(the condylar theory) or at the myo-co(the neuromuscular theory). There is also much controversy regarding the antero-posterior position of myo-co. The object of this study was to measure and compare with the positional relations of centric relation, centric occlusion and myo-co, and free-way space using Mandibular Kinesiograph and Myo-monitor in the 40 subjects without stomatognathic problems. Mandibular Kinesiograph(M.K.G.) was originally conceived as a research instrument to track mandibular movement and position. As its use in research progressed, its great diagnostic value became apparent in case by case. And Myo-monitor was developed as a means of applying the neuromuscular approach to occlusion. Thus the Myo-monitor technique is an intra-systemic approach to occlusal positioning using patient's own musculature, and Myo-monitor is used to relax the musculature by a light myopulse induced electronically. From this experiment, the following results were obtained. 1. The adaptive free-way space before muscle relaxation was an average of $1.6{\pm}60mm$, and the true free-way space after muscle relaxation using Myo-monitor was an average of $2.4{\pm}0.74mm$. 2. It took an average of $25{\pm}3.11$ minutes to relax the mandibular musculature by Myo-monitor and administration of 5mg. Diazepam and an average of $38{\pm}4.73$ minutes by Myo-monitor without administration of Diazepam. 3. Myo-co existed anterior to centric occlusion, with an average of $0.53{\pm}0.31$ mm, and centric relation existed posterior to centric occlusion, with an average of $0.57{\pm}0.58mm$ before muscle relaxation and with an average of $0.57{\pm}0.43mm$ after muscle relaxation. 4. Centric relation coincided with centric occlusion in 5 of 40 subjects(12.5%), and posterior to centric occlusion in the rest of cases (87.5%). 5. Myo-co existed anterior to centric occlusion in 38 of 40 subjects(95%), except 1 subject that coincided with centric occlusion and 1 subject that existed posterior to centric occlusion. 6. Myo-co and centric relation existed inferior to centric occlusion and the lateral displacement was various with individual difference. 7. The total displacement from centric occlusion to centric relation was an average of $0.74{\pm}0.64mm$ before muscle relaxation, and an average of $0.68{\pm}0.53mm$ after muscle relaxation, and the total displacement from centric occlusion to myo-co was an average of $1.07{\pm}0.58mm$.

• The korean journal of orthodontics
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• v.8 no.1
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• pp.59-71
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• 1978

The author compared and analysed the roentgenocephalograms of one hundred Korean adults with the normal occlusion (50 males and 50 females), which were taken on the centric occlusion and the rest position of the mandible respectively for every subject, and then researched the relations among the relaxed muscle of the mandible, lightly touched of the lips, and the position just after the swallowing of saliva, of which 38 among 50 males had the rest position of the mandible. The results are as followings: 1. The anterior facial height increases more at the rest position of the mandible than at the centric occlusion, while the posterior facial height decreases. 2. The mandible moves more backward and downward at the rest position of the mandible than at the centric occlusion. 3. The facial procumbency and the incisor tooth inclination increases more at the rest position of the mandible than the centric occlusion in terms of the facial plane. 4. There are no differences between males and females at the rest position of the mandible and the centric occlusion in the meaning of variation. 5. There are no differences among the three methods from the view of lines and angles of the roentgenocephalogram.

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.945-956
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• 1994

In the past the jaw and occlusal relationship in centric occlusion were merely considered in case of orthodontic diagnosis and treatment planning. As the fact that functional disturbance of the temporomandibular joint may be caused by occlusal interference was recognized, the importance of functional occlusion and centric relation is emphasized today. Known the importance of centric relation, there are various opinions about definition of centric relation and its taking methods. The purpose of this study was to investigate the relative centric condyle position and to compare the reproducibility of the recordings utilizing different centric relation records obtained by different taking methods. The 15 adults with normal occlusion were participated in this study. Every four centric relation records were taken in each of three methods - leaf gauge, Dawson and myomonitor method. Then the relative centric condyle position, the distance between the condylar position in centric occlusion and the position in centric relation and the reproducibility were studied using SAM 2 articulator and mandibular position indicator. The results were as follows ; 1. The trend of condyle position was different depending on centric relation taking methods. 2. The position of condyle in centric relation by leaf gauge and Dawson methods was superior to that by myomonitor method, and the position by myomonitor method was relatively antero-inferior. 3. The distance between the condylar positions in centric occlusion and the position in centric relation was longest in myomonitor method. 4. The reproducibility had little differences in transverse direction among three methods, while leaf gauge method showed the highest reproducibility and myomonitor method did the lowest reproducibility in antero-posterior and supero-inferior direction.

• The korean journal of orthodontics
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• v.21 no.3
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• pp.591-601
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• 1991

To determine the difference in cephalometric measurements between centric relation and centric occlusion, 60 patient-20 patients for each malocclusion group-were examined with the cephalograms in centric relation and in centric occlusion. The results are as follows: 1. There are differences in cephalometric measurements with the mandible in the two different position, and some measurements are statistically significant. 2. No clinically useful prediction may be made from cephalometric radiographs concerning the amount of mandibular deflection from centric relation to centric occlusion. 3. If, the large differences in the cephalometric measurements with the mandible in the two different position, the analysis with the cephalogram in centric occlusion is needed to be compensated with the other clinical approach.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.89-107
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• 1992

The purpose of this study was to investigate the difference between normal and malocclusion subjects in Temporomandibular joint. This study was based on the 44 subjects with normal occlusion, 30 subjects with Class II malocclusion, 30 subjects with Class III malocclusion before treatment. After submental vertex view analysis, each subject was given the TMJ Tomogram in centric relation and centric occlusion and the Cephalogram was taken with Quint Sectograph. The TMJ spaces were measured and analyzed statistically. Following results were obtained. 1. When centric relation was compared to centric occlusion, The condyles were positioned more posteriorly and superiorly in centric relation position of the normal occlusion group and the class II malocclusion group. In the Class III malocclusion group. There was no significant difference in the condylar position between centric occlusion and centric relation. 2. The condyles of the Class III malocclusion group were positioned more superiorly than the normal occlusion group and the Class II malocclusion group. 3. In the correlation between articular eminence posterior slope angle and lingual slope angle of the upper anterior central incisor, there was significant correlation in the normal occlusion group. But no significant correlation was found in the malocclusion group. 4. The mean value of the horizontal angulation of condylar head to the transear rod axis plane was $20.32^{\circ}{\pm}8.12^{\circ}$ in the normal occlusion group, $25.08^{\circ}{\pm}4.83^{\circ}$ in the class II malocclusion group, $14.68^{\circ}{\pm}4.08^{\circ}$ in the class III malocclusion group.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.16 no.1
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• pp.69-79
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• 1986

The purpose of this investigation was to know correlation of mean values between centric occlusion and centric relation by the cephalogram in Angle's Class Ⅰ and Ⅲ malocclusion subjects. 22 adults with Angle's Class Ⅰ malocclusion (17 men and 5 women, 21 to 27 years of age) and 14 adults with Angle's Class Ⅲ malocclusion (10 men and 4 women, 21 to 27 years of age) were selected from the dental students in Yonsei University. Each subject was given two lateral cephalometric radiographies and cephalometric analysis was performed. All data from these analyses was recorded and statistically processed with CYBER computer system. 1. The results were obtained as follows: There was a strong positive correlation between centric occlusion and centric relation in all subjects with Angle's Class Ⅰ and Ⅲ malocclusion. 2. In Angle's Class Ⅰ malocclusion, measurements in lower facial height revealed significant difference between centric occlusion and centric relation (P<0.05). In Angle's Class Ⅲmalocclusion, measurements in facial axis angle, mandibular plane angle, convexity of A point, lower incisor protrusion, lower facial height revealed significant difference between centric occlusion and centric relation (P<0.05). 3. When the mandible was moved from centric occlusion to centric relation, the mean distance of mandibular movement was 1.27㎜ (0.2-2.8㎜) in Angle's Class Ⅰ malocclusion, 1.70㎜ (0.55-4.15㎜) in Angle's Class Ⅲ malocclusion, and 1.44㎜ (0.2-4.15㎜) in all subjects.

• The korean journal of orthodontics
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• v.16 no.1
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• pp.85-106
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• 1986

The purpose of this investigation was to know the means of the T.M.J. space and to compare spational differences in centric relation and centric occlusion by the T.M.J. Tomogram and to study the correlation between the articular eminence slope and the lingual surface slope of the maxillary central incisor by the Cephalogram in near normal occlusion subjects. These results could give contribution for the diagnosis of orthodontic treatment and T.M.J. dysfunction and the assessment of orthopedic treatment and orthognathic surgery. 44 young adults (28 men and 16 women, 21 to 27 years of age) were selected from the Dental students in Yonsei Univ. Criteria for selection was normal occlusion, no clinical signs and T.M.J. dysfunction, no history of orthodontic treatment, and no missing tooth. After submental vertex view analysis. each subject was given the T.M.J. Tomogram in centric relation and centric occlusion and the Cephalogram was given with Quint Sectograph. All data was recorded and statistically processed with the CYBER computer system. Results were analyzed: the following findings and conclusions were derived. 1. The mean value for the combined right and left anterior joint space was 2.549mm, the posterior space was 2.260mm, and superior space was 3.31mm in centric relation. The anterior space was 2.316mm, posterior space was 2.474mm, and superior space was 3.435mm in centric occlusion. 2. In the centric relation position, both condyles were placed more posterioly and superioly in their fossae than in the centric occlusion position by the spatial difference. 3. In the centric occlusion position, both condyles were more symmetrically placed in their fossae with equal anterior-posterioly rather than in the centric relation position. 4. The mean articular eminence angle was $48.19^{\circ}$ and the mean fossa height was 7.911mm. A strong positive correlation between the articular eminence angle and fossa height in T.M.J. Tomogram was found. 5. In Cephalometric analysis, there was a strong positive correlation between the articular eminence slope and the lingual surface slope of the upper central incisor to the FH plane, occlusal plane, and S-N plane. 6. There was moderate positive correlation between the S-E measurements and the fossa height, articular eminence angle, and DcGn < F-H.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.12 no.1
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• pp.15-20
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• 1982

The purpose of this study was to investigate the normal range of condylar displacement of normal adults. The author has observed two roentgenographic images of condylar head taken by transcranial projection. Two roentgenographic images are centric occlusion and centric relation. The results were obtained as follow: 1. Total subjects are 72 condyles. The condylar displacement from centric relation to centric occlusion was shown in 65 condyles (90%) anteriorly. 59 condyles (82%) inferiorly. Two condyles (3%) showed neither anterior displacement nor inferior displacement. 2. The average displacement of right condyles was 0.54±0.06㎜ anteriorly, 0.34±0.05㎜ inferiorly. The average displacement of left condyles was 0.74±0.09㎜ anteriorly, 0.45±0.05㎜ inferiorly. 3. The subjects of synmetrical displacement are 7 cases (20%) anteriorly, 2 cases (6%) inferiorly.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.18 no.1
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• pp.203-212
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• 1988

This study was designed to observe mandibular condyle shape and position in an asymptomatic popular ion. Using Accurad-200 head holder(Denar Corp.) for transcranial radiography of the temporo-mandibular joint region, transcranial radiographs were taken at the centric occlusion and 1 inch mouth opening in 73 males and females who were asymptomatic for TMJ disturbances, had no severe carious or missing teeth, and no history of prosthodontic or orthodontic treatments. Mandibular condyles were classified morphologically at the centric occlusion and evaluated in positional relationship with mandibular fossa and articular eminence at the centric occlusion and 1 inch mouth opening. The results were as follows: 1. In the morphologic classification of mandibular condyle, the convex shape was more prevalent in an asymptomatic population(90.4%), the locally concave shape and wedge shape were 5.5%, 4.1%. 2. At the centric occlusion, the means of joint space were 3.43nm superiorly, 2.17㎜ anteriorly, and 2.61㎜ posteriorly. 3. At the centric occlusion, the mandibular condyles were placed slightly anterior to the center of their fossa. 4. At the 1 inch mouth opening, the mandibular condyles were placed anterior to the articular eminence more than posterior to or below the top of the articular eminence.

• The Journal of the Korean dental association
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• v.22 no.10 s.185
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• pp.869-877
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• 1984

An objective examination of 123 subjects aged from 19 to 23 was made from a clinical standpoints to determine the natural occurrence in anterior tooth contact in centric occlusion, and tooth contact in protrusive occlusion, left and right lateral excursions, and temporomandibular dysfunction. 1. In centric occlusion, maxillary 6 anterior contact type was frequently observe (30.08%) compared with other types of contact (incisor contact: 19.47%, no contact: 17.70%, canine and incisor contact: 15.04%, canines contact: 12.39%, unilateral canine contact: 5.31%) (P<0.01) 2. In protrusive position (edge to edge bite), maxillary central incisors contact was predominant (86.7%). (P<0.01) 3. In lateral excursion, there was not any significant difference between canine guided occlusion (47.79%) and group function occlusion (total 51.32%, AG:9.29%, PG:13.27%, G:28.76%). 4. Temporomandibular joint dysfunction was observed in 12.4% of 123 subjects.